The present invention relates to a process of converting polluting particles emitted in chemical or physical procedures, and in particular to particles comprising environment-polluting metals, into harmless substances.
It is known per se that in several chemical or physical procedures particles escape comprising environment-polluting substances. Most of these polluting particles are caught and stored.
Chemical and physical processes relate in this case also to combustion of fuel, for instance in blast furnaces where the emitted particles are substantially light ash particles.
A disadvantageous result of storing environment-polluting particles, comprising finely powdered metals or metal compounds, is that the latter substances will be lixiviated and will consequently pollute the soil and/or ground water. In view of the ever increasing demands upon the quality of ground water and soil, a lixiviation of substances or other compounds from polluting particles into ground water is inadmissible, the more so when the stored polluting particles comprise finely powdered metals or metal compounds being environment-polluting, such as zinc, cadmium, copper and the like.
Efforts have been made to recycle said particles by chemical or physical procedures, but in most cases this has proved to be impossible. This applies particularly to dust emitted when processing iron-ore into ore-pellets in a blast furnace. Said emitted dust comprises large amounts of zinc, cadmium or copper. Efforts to recycle these metals in the blast furnace have been in vain since the quality of ore-pellets so produced is unsatisfactory. A recycling of the emitted dust in sintering plants where ore-pellets are sintered has proved to be impossible also, because zinc, for instance, accumulates.
Furthermore, efforts have been made to use the caught particles emitted in chemical or physical processes as fillers in fluid bituminous products, but this has the disadvantage that mixing them with bitumen is extremely difficult.
It is an object of the present invention to provide a process of converting polluting particles emitted in chemical or physical processes into harmless substances not presenting the abovementioned disadvantages, whereby, more particularly, the caught polluting particles will be converted into an entirely harmless form.